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Dolly Stability

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#1 JOEinCO

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Posted 17 February 2019 - 07:06 AM

Hello Group.... 

 

A friend has asked for help, but I have no experience with the equipment he is considering. I have a question for people using a dolly to move their scopes into position for observing.

 

I see many designs where the dolly ultimately sits on three threaded leveling rods as shown in the picture below.

 

To me it seems like a terrible base to put an excellent mount on. Any stability inherent to a heavy, quality mount now has to rely on 4"-5" of spindly 1/2" rod. It just seems like one is throwing everything a solid mount has to offer right out the door by using one of these. Any solid triangulation of the mount is then placed on three thin, unbraced "stilts".

 

Can some of you comment on the use of dollies with this design?

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#2 RunningMan

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Posted 17 February 2019 - 08:45 AM

I use a ScopeBuggy and found that stability greatly improved by using the wingnut and washer trick suggested in this thread: https://www.cloudyni...buggy-upgrades/

My setup is plenty heavy, probably 150#, or more, including pier, mount with counterweights, side-by-side scopes (4” refractor + C11), cameras, filter wheel, flattener, etc. I image in my driveway, and rather than run the leveling bolts into my driveway, which would damage the driveway, I place penny-modified rubber vibration isolation pads beneath the leveling bolts. With the bolts in position and the wingnuts tightened, everything is very solid, with no movement or sign of flexure when imaging unless winds become very gusty. Could stability be improved? I bet it could. Is improvement practically needed? Not in my opinion.

Clear skies!
Aaron

#3 JOEinCO

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Posted 18 February 2019 - 01:30 PM

So nobody else has any thoughts about putting a nice solid CGEM-class mount on three "chopsticks"?


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#4 BinoGuy

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Posted 19 February 2019 - 04:52 PM

Oh absolutely, I expect most everyone agrees with you.  The reason some do it is (variously), too many trips/ too much time to assemble a rig, unable to assemble a rig by themselves, or the need to move the rig around the site throughout the observing session due to obstructions.  We all make compromises.  Personally, in addition to the stability problem you mention I think imagers would have issues with realigning to the pole if they move the rig.



#5 santafe retiree

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Posted 20 February 2019 - 02:06 PM

I recently had a local welder fab me a "one off" of a dolly based on the Scope Buggy design at 1/2 the cost.  I prefer the pneumatic tires of the Scope Buggy over the hard rubber casters of the JMI design because I did not like the rough ride of the casters.

 

One of the mods was to put 1/2" PVC pipe end caps on the ground end of the "leveling" rods.  That keeps the rods from marring my driveway.  The caps also provide a wider base for the rod end.

 

The PVC pipe "T" at the other end are a nifty way to raise and lower the "leveling" rods.

 

To answer your question about stability, I don't use the "leveling" rods to lift the dolly off the ground. I only use them to prevent the dolly from shifting.  The actual leveling is done with my iOptron Tri-Pier if in fact any leveling is needed.

 

Steady air,

 

Tom

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#6 JOEinCO

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Posted 20 February 2019 - 07:44 PM

.....To answer your question about stability, I don't use the "leveling" rods to lift the dolly off the ground. I only use them to prevent the dolly from shifting......

So now the stability of a heavy duty mount is relying on pneumatic tires and their inherent flex?? confused1.gif 

 

I don't get it.

 

I guess I would need to see one in use to convince myself that a dolly isn't a detriment. Unfortunately, all the public events I've ever been to are held on grass fields, and dollies aren't exactly "transport your scope in your vehicle" widgets. JMI used to be 10 miles away; I guess my friend and I missed our chance to answer this question for ourselves.... wink.gif 

 

Thanks for your responses.



#7 santafe retiree

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Posted 20 February 2019 - 11:43 PM

Well that is not quite how it works -- things like the total surface area of all six points of contact, cross torsional stability of all six points of contact, inertia, mass of not only the mount and scope but the added mass of the dolly (50 lbs)  --  they all play a role  -- but I agree that you should  see one for yourself -- good luck


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#8 RunningMan

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Posted 21 February 2019 - 08:36 PM

Hi JOEinCO,

For me, a permanent setup is not feasible, and before I started using a scope-buggy I was spending too much time assembling and disassembling my  setup each time I wanted to do some imaging or viewing. This extra assembly/disassembly time resulted in many a missed imaging/viewing opportunity. And with such opportunities a rarity, here in Michigan, I decided to try a mobile setup, which I could leave fully assembled in storage and pull out into the driveway. Now set up takes about ~15 minutes, including polar alignment (Polemaster), after which imaging can immediately commence. As I mentioned in my previous message, I place hard rubber vibration isolation pads (like those used for a washing machine) on my driveway beneath the bolts, with holes bored part of the way through the pads to hold a penny (to accept each bolt, so that it doesn't destroy its vibration pad). I use the bolts to lift the entire setup off the ground, just high enough that tires spin freely. For comparison, when I was doing full setup/teardown, I was using a sturdy Takahashi tripod. I now use a pier mounted to the scope-buggy and I have noticed no decline relating to flex/stability of the system (or trailed stars), so long as I tighten the wing nuts to lock down the bolts.

Clear skies!

Aaron


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#9 Alien Observatory

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Posted 21 February 2019 - 08:58 PM

My Scope Buggy "ran away" and crashed...luckily only destroyed my Nikon D5500 ($550 replacement cost)...So I use 1/4" bungie cord to hold it down now...if I could make metal straps that would be better...so maybe a garage project while the snow flies...and I have added 45 lbs of lead shot inside the tripod legs to move the CG lower as a further precaution...  Pat Utah smile.gif

 

Link to Buggy Disaster...

https://www.cloudyni...le-nikon-d5500/

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#10 TxStars

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Posted 22 February 2019 - 05:05 PM

Placing anything that is tall or top heavy on rollers is never a great idea.

Can it be done? sure anything can be done.

Is it right for you? perhaps?

 

I listed some things to think about.

 

1) Is the tripod/pier attached firmly to the roller base

2) are the rollers/wheels wide enough apart to prevent tipping

3) are you rolling on a smooth surface.

4) are you rolling on a flat surface



#11 tsbikes

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Posted 22 February 2019 - 08:54 PM

Similar to Aarons setup I have a modified Scope Buggy. First I have 3 threaded rod of 1/2" diameter for jack stands. The Buggy has 1/2 nuts welded  on for these rods and I added nuts that can be tightened make these stands more rigid. I also welded nuts  to the top of the rod so the jack stands can be adjusted with a Battery powered drill for leveling. I also fasten the tripod to the buggy with heavy duty double faced Velcro straps. These have not loosened over three years of use.

My process is to roll out the fully equipped scope to a predetermined site aligned with south. Level with the jack screws. Goto a bright star and sync. And I am set for the night. Most Gotos are on the eyepiece. I get no wobble unless I get clumsy and trip over the rig.

I think the secret is the locknuts tightened to the buggy mount nuts. I also turned a point on the jackscrews so they don't wobble on the concrete and I use 3" x 3" rebar pads under them when on soft surfaces.

I will provide pictures if anyone is interested.

I also drilled and tapped the main T section of the Buggy so I can drive a screw through it to lock the sliding wheel mounts in place.

 

Jim




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